The commercial cat litter industry has undergone substantial change since the introduction of clumping bentonite clay cat litters as disclosed in the Hughes U.S. Pat. No. 5,000,115, hereby incorporated by reference. As disclosed in the Hughes '115 patent, bentonite clay cat litter that is wetted with cat urine will agglomerate into a clump having sufficient structural integrity so that the agglomerated clump can be removed from a cat litter box, thereby removing the cat urine, as well as feces, with a slotted scoop. The remainder of the unsoiled cat litter material can remain in the litter box for reuse without generation of odor over substantial periods of time of one year or more.
Some of the patents that disclose the use of clay as an absorbent pet litter material are as follows: Crampton, et al. U.S. Pat. No. 4,657,881; Stuart U.S. Pat. No. 4,685,420; McFadden U.S. Pat. No. 3,286,691; Japanese published patent applications J5 8009-626, J6 3044-823-A; J6 0094-043-A; J6 3185-323-A, J6 2239-932-A, and JO 1191-626-A; German DE 3620-447-A; Ducharme, et al. U.S. Pat. No. 4,844,010; Kumar U.S. Pat. No. 4,343,751; and Jaffee, et al. U.S. Pat. No. 4,459,368. The following U.S. patents teach pet litters that include additives, e.g., polymers for clumping, or odor control additives: U.S. Pat. No. Lang U.S. Pat. No. 4,736,706; Smith U.S. Pat. No. 4,671,208; Stuart U.S. Pat. No. 4,685,420, Sowle, et al. U.S. Pat. No. 5,014,650; and Nelson U.S. Pat. No. 5,062,383.
In addition to a good portion of the cat litter industry moving toward the use of clumping bentonite clay cat litters, others have attempted to provide additional improvements to cat litter material for the purpose of providing a home diagnostic means and/or a home animal health monitoring means to quickly monitor the health of a cat at home, by the use of feline urine screening tests. One of these home feline urine screening tests presently is marketed under the trademark CATSCAN.TM.--a finely divided solid substance that is sprinkled from a package onto the surface of the cat litter from one of four different packages, each having an indicator dye indicative of one of: blood, pH, protein or glucose contained in the cat urine.
Another commercial cat litter product, called FUSSY CAT D, is a clumping, clay cat litter material that includes a pH-indicating dye bound to the clay material during manufacture of the cat litter and having a color transition at an a alkaline pH indicative of feline urologic syndrome.
U.S. patents uncovered that disclose the use of a pH indicator in connection with an absorbent product or a polymeric substance include Seidenberger U.S. Pat. No. 3,994,821; Rohowetz U.S. Pat. No. 4,179,397; Tratnyek U.S. Pat. No. 4,407,960; and Marsoner, et al. U.S. Pat. No. 4,587,101. Mandel, et al. U.S. Pat. No. 4,865,761 discloses mineral-based, clay-containing absorbent material for absorbing hazardous, acidic spills. Hamm, et al. U.S. Pat. No. 4,925,826 discloses a mineral-based absorbent material for the absorption of animal excrement. Gruss U.S. Pat. No. 4,326,481 discloses a granular material useful in taking a urine sample from a cat; Nugent U.S. Pat. No. 4,827,944 and Seidler, et al. U.S. Pat. No. 3,774,455 disclose urine collection and testing devices.
One of the problems associated with combining one or more pH-indicating dyes with a clay-based cat litter material is that clay litter materials include a number of exchangeable metallic cations and other chemical species that, when in contact with cat urine, may alter the pH of the cat urine, or otherwise interfere with the color transition of indicator dyes within the pH range that a color transition should be indicated, thereby providing false urine pH information. Further, attempts to provide pH indicators as a coating material onto the surface of clay cat litter material during manufacture have not been entirely successful since the dyes, particularly the water-soluble dyes that are indicative of pH of cat urine within a desired pH range, are substantially absorbed into the interior of the clay particles and, therefore, any color transition that occurs within the interior of a clay cat litter particle is difficult if not impossible to perceive visually, particularly for the water-swellable bentonite clays.
The pH-indicating materials and the cat litter material containing the pH-indicating materials of the present invention overcome the deficiencies of the pH-indicating cat litter materials of the prior art by providing the pH indicator(s) within a dried film of water-soluble polymer dried onto a solid, inert carrier material. In this manner, when the film coating on the inert carrier material is wetted with cat urine, the urine penetrates the polymeric film and the water-soluble pH-indicating dye(s) are solubilized within the cat urine to provide an easily detectable color transition on the surface of the inert carrier material without interference from any pH interaction or dye interaction from the cat litter material itself.